- Reflecting on Higgs: Spin and parity measurement in the H → WW → eνeμνμ channel
- Award date
- 27 September 2016
- Number of pages
- Document type
- PhD thesis
- Faculty of Science (FNWI)
- Institute for High Energy Physics (IHEF)
To test if the discovered particle in 2012 at LHC’s ATLAS and CMS experiments is indeed a Standard Model (SM) Higgs boson, its spin and CP quantum numbers have to be measured. A SM Higgs boson should be a spin-0 particle and stays invariant under charge-parity (CP) operations. Spin is an internal quantum number related to angular momentum and CP plays an important role in weak nuclear processes, such as radioactive decay. Both quantum numbers should be conserved; meaning that the final decay products of the Higgs boson, an electron (e), a muon (μ) and neutrinos (ν), have constraints on their kinematics. The analysis presented in this thesis exploits these kinematic constraints to not only test the SM prediction, but also various other models, which allow for a spin-2 particle, CP-odd/even spin-0 particles and mixtures between a SM Higgs boson with another CP-even or CP-odd spin-0 particle. The results have been obtained by using 2012 data collected with the ATLAS detector from conducting proton-proton collisions at a center-of-mass energy of 8 TeV. It turns out that the data shows a preference for a spin-2 particle above the SM prediction of spin-0. However, this result is not significant enough to claim an observation or even a discovery. Various crosschecks have shown that the SM prediction is still compatible with the 2012 data set and more data is needed to see if the spin-2 preference in the H→WW→eνμν channel persists.
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